Electrode material for a spark plug

Abstract

An electrode material for a spark plug 10 for use in an internal combustion engine. The electrode material includes a core 20 having a high thermal conductivity for reducing the temperature of the spark plug 10 by thermally conducting heat away from the spark plug gap to a cooler part of the engine. The core 20 extends continuously from an arcing surface at an end of a spark plug electrode to the cooler part of the engine. Surrounding the core 20 is a cladding layer 22 for resisting corrosion when exposed to high temperatures caused by arcing.

What is claimed is: 
     
       1. A spark plug for use in an internal combustion engine, the spark plug having a center electrode, a ground electrode, each electrode having a hot end and a cooler end, the cooler end being in thermal communication with the engine, a gap defined between the center and ground electrodes, and a shell, wherein at least one of the ground and center electrode includes an electrode material with: a core having a high thermal conductivity for reducing the temperature of the spark plug by conducting heat away from the gap, the core extending continuously from an arcing surface at the hot end of the at least one of the ground and center electrodes to the cooler end of the other one of the ground and center electrodes;   at least one cladding layer consisting essentially of a metallic material selected from the group consisting of a metal, an alloy, and mixtures thereof, the cladding layer being metallurgically bonded to the core for resisting erosion when exposed to high operating temperatures of the engine and   a diffusion interlayer between the cladding layer and the core, the diffusion interlayer comprising a metallurgical bond at least adjacent to the gap between the center and ground electrodes for promoting heat transfer and minimizing delamination of the cladding layer from the core.   
     
     
       2. The spark plug of claim 1 wherein the core comprises a metallic material. 
     
     
       3. The spark plug of claim 1 wherein the core is selected from a group consisting of copper, nickel, iron, silver, alloys thereof, aluminum nitride, and graphite. 
     
     
       4. The spark plug of claim 1 wherein the core comprises a stranded construction of high thermal conductivity strands proportionately mixed with strands of a high oxidation resistance alloy to resist oxygen attack and promote thermal conductivity. 
     
     
       5. The spark plug of claim 1 wherein the hot end of the at least one of the ground and side electrodes includes a cap joined to the hot end in order to provide greater resistance to oxidation and thus loss of material by spalling. 
     
     
       6. The spark plug of claim 5 wherein the cap comprises a copper nickel chromium iron alloy. 
     
     
       7. The spark plug of claim 1 wherein the core comprises up to 70% of the cross-sectional area of the at least one of the ground and center electrodes. 
     
     
       8. The spark plug of claim 1 wherein the cladding layer is a layer which comprises multiple sheets of cladding. 
     
     
       9. The spark plug of claim 8 wherein the layer comprises an inner cladding layer selected to alloy easily with copper, resulting in an oxidation-resistant alloy when fusion welded, and an outer cladding layer providing an arc-resistant surface. 
     
     
       10. The spark plug of claim 1 wherein the center electrode comprises a consumable welding electrode which caps the hot end thereof and provides an arc-resistant surface. 
     
     
       11. The spark plug of claim 1 wherein the center electrode comprises the electrode material. 
     
     
       12. The spark plug of claim 1 wherein the ground electrode comprises the electrode material. 
     
     
       13. The spark plug of claim 1 wherein the center electrode and the ground electrode are formed from the electrode material. 
     
     
       14. The spark plug of claim 1 wherein the at least one electrode has a circular cross-section. 
     
     
       15. The spark plug of claim 1 wherein the at least one electrode has a generally rectangular cross-section including rounded corners joining adjacent sides. 
     
     
       16. The spark plug of claim 1 wherein the electrode material has a cross-section having a shape selected from the group consisting of triangular, trapezoidal, and half-round. 
     
     
       17. The spark plug of claim 1 wherein the cladding layer comprises an alloy selected from the group consisting of a nickel-based alloy, a cobalt-based alloy, an iron-based alloy, and mixtures thereof. 
     
     
       18. The spark plug of claim 1 wherein the cladding layer consists essentially of an alloy, the core comprising a ceramic material having a high thermal conductivity approaching the thermal conductivity of pure copper while obtaining the oxidation-resistant characteristics of precipitates. 
     
     
       19. The spark plug of claim 1 wherein the core comprises a copper alloy including an alloying element which can be precipitated through heat treatment, thus approaching the thermal conductivity of pure copper while obtaining the oxidation resistant characteristics of the precipitates. 
     
     
       20. The spark plug of claim 18 wherein the core consists essentially of a copper, chromium, titanium alloy or copper alloys with limited solubility additives that can be heat-treated to precipitate out secondary phases, thus approaching the thermal conductivity of pure copper while obtaining the oxidation-resistant characteristics of the chromium and titanium precipitates. 
     
     
       21. A spark plug with a center electrode and a ground electrode, each having a hot end and a cooler end, the cooler end being in thermal communication with an internal combustion engine: wherein the ground electrode has a composite electrode material with:   a core of a high thermal conductivity for reducing the temperature of the spark plug by thermally conducting heat away from a gap defined between the ground electrode and the center electrode, the core extending continuously from an arcing surface at the hot end of the ground electrode to the cooler end of the ground electrode;   a cladding layer of a metallic material surrounding and metallurgically bonding with the core for resisting erosion when exposed to high temperatures caused by arcing; and   a diffusion interlayer between the cladding layer and the core, the diffusion interlayer comprising a metallurgical bond at least adjacent to the gap between the center and ground electrodes for promoting heat transfer and minimizing delamination of the cladding layer from the core.   
     
     
       22. The spark plug of claim 21 wherein both the ground electrode and the center electrode are manufactured from the composite electrode material.